The 21-year-old actress is currently participating on the US version of Dancing with the Stars.

Sasha Pieterse is letting fans in on her weight gain struggle.

The 21-year-old actress, who found fame as Alison DiLaurentis on Pretty Little Liars, is currently participating on the US version of Dancing with the Stars.

And on Monday night, the star -- who was dancing the Samba to Hailee Steinfeld's body-confident anthem 'Most Girls' -- broke down in tears as she opened up about gaining 32 kilos over the course of two years.

"I love the song because it really resonates with me about what I've been through, and what I'm still going through," Sasha told her pro dance partner Gleb Savchenko during their filmed rehearsals. "I gained 70-ish pounds over two years."

For Sasha, who was in her teens at the time, the criticism was rife.

"It was really, really hurtful the way people reacted," Sasha said. "They were saying stuff like, 'She's pregnant.' 'You're fat.' They were angry, they were mad that I look like this. It was one of the hardest things I've ever been through."

The actress had no idea what was the cause of her weight gain until 2015, when she was diagnosed with a hormone imbalance called Polycystic Ovary Syndrome.

Since then, she's made it her mission to encourage others to embrace their insecurities and love themselves.

"We’ve all heard our parents tell us to treat people the way you want to be treated, but I think often we don’t treat ourselves the way we should be treated," she wrote in a 2016 Twitter statement. "Do not lower yourself to people who refuse to grow higher. If you don’t love yourself, you’ll continue to chase people who don’t love you either."

Now, Sasha has already lost 6 kilos on her Dancing with the Stars journey.

"It's not an easy road," she explained on the show. "But being able to focus on getting myself healthy again and the fact that I'm seeing results now and getting better is all I can ask for."

In other exciting news, Sasha is set to reprise her Pretty Little Liars' role as Alison when she joins the upcoming spin-off, The Perfectionists. She will be joined by Janel Parrish, 28, who starred as Mona Vanderwaal on PLL.